Putting in contact various fluids with one another, appearing in the form of at least one hot and gas phase, and of liquid phases, semiliquid phases or pasty phases containing or not containing solid materials in suspension, has raised numerous difficulties for the art for a long time. This problem is encountered in a good number of applications, such as, for example, the treatment of waste acids, residual waters or also the drying of solid materials in suspension in a liquid phase. In any case, the treatment consists in subjecting the liquid or the suspension to the action of a gas brought to high temperature, such as combustion fumes or hot air, so that by the twin action of a heat transfer and a mass transfer, there would be a reaction between the gas phase or phases and the liquid phase resulting in the evaporation or the decomposition of the liquid and a separation of the solid particles which can thus be recovered after a modification of their surface state. Carrying out of such a treatment necessitates the achievement of as thorough a contact as possible between the various phases present so as to achieve a heat transfer from the hot and gas phase to the liquid phase with maximum efficiency.
Various devices have been proposed to achieve this. In particular, in French Patent No. 2 257 326 a process has been described for putting in contact substances appearing in different phases, one being gas, the other to be dispersed such as a liquid, solution or suspension. This process consists in:
imparting to the gas phase a swirling helical movement before this phase is mixed with the liquid phase to be dispersed, PA1 feeding the liquid phase into a rectilinear current coaxial with the axis of symmetry of the gas phase, PA1 imparting to this gas phase a quantity of movement much greater than that of the liquid phase to be dispersed, sufficient to cause at the point of impact, at the same time, the dispersion of this phase and its takeover by the gas phase. PA1 the gas flow near its impact with the liquid phase has a perfect symmetry around its axis of revolution, and PA1 the position of this impact in the vicinity of the narrow space is geometrically well defined in the space and remains unaffected by the temperature differences. PA1 first, a poor symmetry of the "vortex sink" flow and the movement of the impact zone between the gas-liquid (semiliquid or pasty) phases, causing a reduction in the effectiveness of the mixture between the phases, PA1 then the direct interception of a part of the liquid jet by the walls of the outlet divergent with, and because of the temperature prevailing on the walls of the chamber, a progressive formation of deposits coming either from the decomposition of the liquid or from the precipitation of the solids carried in the suspension, PA1 finally, the occlusion of the chamber for separation of the phases, a result of the gradual and irregular feeding of its wall which in turn causes an accentuation of the lack of balance of the flow at right angles with and at the outlet of the throat.
Thus, a contact as thorough as possible is obtained facilitating the reaction between the two phases.
The treatment is of the flash type and can be accompanied by a high difference in temperature between the two phases.
In this same patent, the means are described and claimed that are to be put into practice to obtain a contacting of the substances.
The proposed device comprises first of all an outer envelope of revolution ending at its lower part with a tapered element whose small base constitutes a circular opening of narrow section and comprising at the upper part a fluidtight wall providing passage to a feed pipe coaxial with the envelope and which is solid with it. The downstream end of this pipe comes out at a distance from the mean plane of the circular opening between 0 and the radius of this opening, the outer section of the inner piping being at most one-fourth of the section of the opening of narrow section.
The proposed device further comprises a means for feeding into the envelope around the coaxial pipe the gas phase to be put in contact, imparting to it a helical movement symmetrical in relation to the axis merged with the feed pipe and with the envelope as well as a container placed contiguously downstream from the envelope constituting a chamber for separation of the phases. The upper part of this container is in the shape of a divergent cone connected by its vertex to the circular opening and its axis of revolution is merged with that of the outer envelope.
In this device, the gaseous fluid in helical movement has its speed grow as it flows in the tapered space delimited by the lower part of the outer envelope and by the feed pipe. This speed is maximal in the vicinity of the passage of the circular opening.
It then gives rise beyond the mouth of this opening to a group of paths distributed along a hyperboloid whose axis is merged with that of the opening. These paths diverge until encountering the walls of the downstream container on which they again generate a pseudohelical movement of rotation. The group consisting the convergent-shaped outlet of the outer envelope of revolution and the divergent high part of the container has the shape of a pipe.
Different variants were conceived afterwards to the device described in French Patent No. 2 257 326 to increase the effectiveness of the contact between the phases and to adapt the operation of the device either to the treatment of hot fluids, or even to a combustion process.
In particular, the application of the process in the case of a combustion is described in French Patent No. 2 276 086.
The fuel substance can enter into the reaction chamber in the gas or liquid state and constitutes the axial rectilinear current. The helical current can consist of gases able to react with the axial rectilinear current. In the case of a combustion, this gas is advantageously air.
The flow and the distribution of the paths of the helical gas current are such that a depression is created in the axial zone of this current at the mouth of the circular opening. This depression has the effect of causing a suction of the axial rectilinear current of the fuel, which has the advantage, while facilitating the mixture of the phases, of limiting the pressure necessary for the injection of this fuel.
The ignition of this fuel is provided by a standard device such as a spark plug between the electrodes from which a spark discharges.
Also, thanks to French Patent No. 2 404 173, a variant of the same device is known comprising coaxially an upstream chamber for flame generation and a downstream (combustion) chamber, the chambers communicating with one another by a narrow zone consisting, for example, of a covergence zone followed by a cylindrical part forming a neck.
In the first upstream chamber for flame generation, a symmetrical "vortex sink" flow with an oxygen-carrying gas is created, a fuel fluid is fed along an axial symmetry, and the formation of a flame is caused.
In the second downstream chamber, a gas phase to be treated is fed into the flame coming from the first zone, the gas phase being able to consist of thermodegradable combustible materials chemically transforming under the action of heat.
Finally, in French Patent No. 2 431 321, an improved device is known in which a combustion is performed in a reaction chamber having at its downstream end a convergent-divergent nozzle, whose smallest section constitutes a narrow passage. A current of hot fumes is generated circulating in a symmetrical helical movement through the narrow passage and fed through a suitable pipe into the partial vacuum zone of the "vortex sink" flow created by the current of fumes, along its axis of symmetry, a liquid, semiliquid or pasty phase.
The feed pipe of the liquid, semiliquid or pasty phase comes out at the height of the narrow space in the axis of revolution of the outer envelope.
The operational effectiveness of such devices intended to put in contact at least two phases one of which is gaseous and hot is governed by numerous parameters, one of the most important of which consists in obtaining a perfect mixture of the liquid, semiliquid or pasty phase fed with the gas phase in movement. This implies that the gas phase exhibits at the point of impact with the liquid phase a sufficient kinetic moment to cause a dispersion of fine droplets of liquid in the gas volume and their takeover by this gas according to a homogeneous distribution, a corresponding volume of fumes being associated with each droplet.
This result can be obtained only on condition that:
In particular, this involves a precise execution of the convergent-divergent nozzle and a strict geometric positioning of the mouth of the feed pipe of the liquid phase in relation to the throat defined by the convergent-divergent nozzle.
Now, in the case of treatments such as, for example, drying or reactions putting into play various phases at least one of which is fed or brought to high temperature, the mechanical behavior of the elements of the device subjected to high temperatures, for example greater than 400.degree. C., is generally affected by stresses due to temperature. If, in a more precise way, there is made to circulate in the outer envelope of revolution a hot gas phase (combustion fumes or hot air) at a temperature at least equal to that previously cited, and the feed pipe is supplied with a liquid, semiliquid or pasty phase at a temperature clearly lower that that of the gas phase, the expansion of the outer envelope causes, as the applicant has been able to establish, a movement of the feed pipe which is solid with it, and particularly of its mouth in relation to the axis and to the plane of the throat of the convergent-divergent nozzle.
Consequently, there have been major drawbacks such as:
Consequently, it has proven essential to avoid, under the action of high temperatures, there being able to be loss of adjustment of the position of the mouth of the feed pipe in relation to the throat of the convergent-divergent nozzle. For this reason, the applicant, pursuing his research in this field, studied and developed an improvement of the devices of the prior art so as to avoid those drawbacks, these improved devices being intended to put in contact fluids appearing in the form of various phases at least one of which in helical movement is in gaseous and hot form.